Use a birthday cake. Click the birthday cake; it should say, "Put birthday candles" (which costs Sim dollars). After you put the candles on, click the option that says, "Blow out candles," and choose whichever Sim you want to grow up.
If these plants came from a conventional garlic seed pod for sure, they're garlic. The curly bits that emerge with "tear drops" you see are actually called garlic scapes and...
You will first have to change your fairy Sim to a normal Sim using the potent cure elixir or the "ask forsake the fae" action with a significant other, then...